<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            margin:0 auto;
        }
        .c2{
            color: red;
        }
    </style>
</head>
<body>
<div class="c1"></div>
<div class="c2 c1"></div>
<div class="c1 c3"></div>
</body>
</html>